Update docs to use vendored version of arrow (#772)

Author: alamb

README.md

@@ -69,8 +69,8 @@ Run a SQL query against data stored in a CSV:
 
 ```rust
 use datafusion::prelude::*;
-use arrow::util::pretty::print_batches;
-use arrow::record_batch::RecordBatch;
+use datafusion::arrow::util::pretty::print_batches;
+use datafusion::arrow::record_batch::RecordBatch;
 
 #[tokio::main]
 async fn main() -> datafusion::error::Result<()> {
@@ -92,8 +92,8 @@ Use the DataFrame API to process data stored in a CSV:
 
 ```rust
 use datafusion::prelude::*;
-use arrow::util::pretty::print_batches;
-use arrow::record_batch::RecordBatch;
+use datafusion::arrow::util::pretty::print_batches;
+use datafusion::arrow::record_batch::RecordBatch;
 
 #[tokio::main]
 async fn main() -> datafusion::error::Result<()> {

datafusion/src/lib.rs

@@ -39,7 +39,7 @@
 //! ```rust
 //! # use datafusion::prelude::*;
 //! # use datafusion::error::Result;
-//! # use arrow::record_batch::RecordBatch;
+//! # use datafusion::arrow::record_batch::RecordBatch;
 //!
 //! # #[tokio::main]
 //! # async fn main() -> Result<()> {
@@ -77,7 +77,7 @@
 //! ```
 //! # use datafusion::prelude::*;
 //! # use datafusion::error::Result;
-//! # use arrow::record_batch::RecordBatch;
+//! # use datafusion::arrow::record_batch::RecordBatch;
 //!
 //! # #[tokio::main]
 //! # async fn main() -> Result<()> {